When connecting a personal computer to a network such as the Internet via a public circuit network, a user accesses an Internet service provider through a so-called dial-up connection. The personal computer can thus browse a web page published on the Internet and send and receive email via the Internet service provider.
The wired connection using cables has been the primary type of connectivity between the personal computer and the public circuit network. Recently, Bluetooth (trademark), which is wireless connection technology, has been drawing attention.
Bluetooth is a wireless transmission system using the 2.4 GHz band. Bluetooth technology uses short-range wireless communication for exchanging information. An object of Bluetooth technology is to easily connect cellular phones, personal computers, PDAs (Personal Digital Assistants), and peripheral devices with one another. Since this wirelss communication uses the 2.4 GHz ISM (Industry Science Medical; which is an unleased band) that can be used worldwide, a device compliant with Bluetooth technology can be used worldwide. For example, using this technology in peripheral devices of a personal computer makes all devices including a mouse, keyboard, modem, and printer wireless. Using Bluetooth technology in connectivity between devices such as a cellular phone and modem for connecting to the public circuit network and a personal computer makes cables, which used to be necessary, unnecessary.
As shown in FIG. 1, a personal computer 1 connects to a Bluetooth adapter 2 using Bluetooth-based short-range wireless communication and, from the Bluetooth adapter 2, connects to the Internet 5 via a public circuit network 3 and an Internet service provider (ISP) 4. The personal computer 1 thus becomes capable of, for example, sending and receiving email or accessing a predetermined web server (not shown) and browsing a web page. Bluetooth-based connectivity between the personal computer 1 and the Bluetooth adapter 2 is always on.
Recently, other than the personal computer 1, so-called mobile devices such as PDAs (Personal Digital Assistants) and cellular phones that the user can carry have been widely used. Such portable and network-connectable devices including these mobile devices are operated by batteries. When these devices are in Bluetooth connection always-on mode, the power consumption is increased, and the batteries are exhausted quickly.